1. Field of the Invention
This invention relates to a parts feeder which sequentially feeds light, small-sized parts such as springs. This invention particularly relates to a parts feeder wherein a conveyance path, along which the parts are conveyed, is prevented from being clogged with the parts.
2. Description of the Prior Art
Parts feeders have heretofore been known as a means for feeding small-sized parts such as torsion springs to various types of assembly apparatuses. The parts feeder conveys the parts along an annular conveyance path, for example, a spiral conveyance path, and a linear conveyance path which is connected to the annular conveyance path. The annular conveyance path is provided with an adjustment means which adjusts, for example, the orientations of the parts sequentially fed from a feed tank and lines up the parts. The parts are thereafter conveyed along the linear conveyance path to the corresponding assembly apparatus. Also, the linear conveyance path is provided with a fill detection means which generates a fill detection signal when the linear conveyance path is filled with the parts. When the fill detection signal is generated, the parts feeder temporarily stops conveying the parts along the annular conveyance path to the linear conveyance path. After the fill condition on the linear conveyance path is eliminated, the parts feeder restarts conveying the parts along the annular conveyance path to the linear conveyance path. However, when the parts which are being conveyed are stopped forcibly or when the parts which are kept stationary are moved forcibly, the parts are vibrated and entangled, and the entangled parts clog the annular conveyance path. Therefore, the parts cannot be fed smoothly to the assembly apparatus.
Accordingly, in order to eliminate the problem described above, compressed air has heretofore been blown against the overall area of the annular conveyance path. Alternatively, several clogging detection means have heretofore been located at positions where clogging arises readily, and compressed air has heretofore been blown against the position where clogging is detected, thereby to remove the clogging parts from the conveyance path.
However, with the technique wherein compressed air is blown against the overall area of the annular conveyance path, parts which have been lined up are often removed from the annular conveyance path together with the parts which are entangled. Therefore, the parts cannot be fed at a constant rate to the assembly apparatus. Also, if the pressure of compressed air were increased markedly, all parts would be removed from the annular conveyance path. Therefore, the pressure of compressed air must be kept at a low level which is insufficient to remove clogging parts.
With the technique wherein a plurality of clogging detection means are used, good effects of removing the clogging parts are obtained. However, since a plurality of clogging detection means and a plurality of compressed air feed means must be provided, the manufacturing cost of the parts feeder increases.